[CitizenKane]

Apologies for posting approximately a thread a week these days...

I've finally settled on a new set of wheels for my e92 (AG M359s in gunmetal), but it has occurred to me that I am completely clueless about tyres.

The wheel specs are:

Front - 19x9 ET35
Rear - 19x10 ET38

I'll be keeping them on stock M Sport suspension (for now).

Question: what sort of tyre profile and width should I be going for?

Thanks in advance.

[Adam1990]

If they're 19's I believe you would probably need some 235/35/19 at the front and some 265/30/19 in the rear and I think that might look slightly stretched.

If it's for an e92 I want to say you might be able to get 245 up front and 275 in the rear but I could be wrong.

[KiwiRD]

I just bought the same wheels in Hyper Silver for my pre LCI E90 M Sport 335i on a B12 kit. I went with 235/35R19 and 265/30R19 for the rear. To minimise the stretch factor, I purposely went for Michelin as they tend to run a wider shoulder than, say, a Falken. I opted for the new Pilot Sport 4S, and while they are slightly stretched (it is almost inevitable there will be some stretch due to the sheer width of the wheels), I'm totally happy with the look.

When you look closely at new cars that are running large wheels, even they have what could be considered stretch - especially cars like the new Golf R etc. Their wheels may not be 9 and 10 inches in width, but they're also running narrower tyres so there is still a little bit of stretch present. It may not be great for ride comfort, but it does help a touch with steering response.

[CitizenKane]

Thanks both.

The picture that made me fall in love with these wheels is below. Obviously my car will never look quite like this because it's an m3 and (I presume) lowered, but the closer I can get to this kind of stance the better...

[Digitalize]

Those are basically the same. You could try 245/35/19 and 275/30/19 but I don't see the need.

[KiwiRD]

Originally Posted by Digitalize

Those are basically the same. You could try 245/35/19 and 275/30/19 but I don't see the need.

I had contemplated those sizes too, but the tyres are a tad heavier than the 235/265 combo, and with the new wheels being a little heavier than the OEMs I wanted to minimise any weight increase. Fortunately the PS4S is a light tyre by comparison to others so the difference wasn't too bad.

[CitizenKane]

Excuse my ignorance (as I said I'm clueless about this), but is there any particular benefit in choosing one tyre width over another? I understand that there is generally a range of tyre widths that can fit rims of a given width, but is there any reason for example to choose a width on the narrower end of the range or the wider end of the range? Will it make any difference to how it performs or looks?

[Digitalize]

It will make a difference to both. Arguably a more visual change than one of driving feel, but changing tyre sizes does effect that also.

[KiwiRD]

Originally Posted by CitizenKane

Excuse my ignorance (as I said I'm clueless about this), but is there any particular benefit in choosing one tyre width over another? I understand that there is generally a range of tyre widths that can fit rims of a given width, but is there any reason for example to choose a width on the narrower end of the range or the wider end of the range? Will it make any difference to how it performs or looks?

The first point to remember is that BMW deliberately engineers its cars to understeer rather than oversteer, as it is considered safer for the average punter. Hence narrower front tyres than rear tyres - less grip at the front than the rear and therefore understeer prevails.

Secondly, despite differing tyre widths and profiles on the front and rear wheels, both share the same rotational circumference, and this must be retained whatever happens when you 'upsize'.

Remember that when you upsize your wheel and tyre combo, the wheel diameter increases and the tyre profile decreases - thus retaining the factory rolling circumference. While it is nearly impossible to retain the precise factory rolling circumference down to the last mm, generally it is advisable to keep this within 1% of the factory figure.

The reason I say all this is that it will to a large extent determine what tyre widths you can run on any given wheel diameter. When moving to a 19" set up from a 225/40R18 tyre on an 18" wheel, the closest match in overall circumference becomes a 225/35R19 - however, as your front wheels are 9" wide (as opposed to the factory 8" width), that size will look very stretched, and the ride will suffer quite a bit. So the next best option is to move up one section width to a 235/35R19, which is still very close to the factory circumference, but provides a slightly better ride on account of a slightly taller sidewall profile.

If you don't know, the tyre measurements are as follows:

225/40R18: 225 is the width of the tyre in mm, the '40' relates to the sidewall height and is a percentage of the tread width, i.e. 40% of 225mm, and the 18 is the diameter of the tyre in inches.

Likewise on the rear - the closest match to a 255/35R18 would ideally be a 255/30R19, however on a 10" wide rear wheel that would be a lot of stretch, so again, you move up one section width to a 265/30R19, or two section widths up to a 275/30R19. Both sizes will fit, though the latter will look slightly less stretched. My preference was to keep the 265/30R19 rear size due to weight (around 1 pound lighter than the 275/30R19) and go for a tyre that has a 'wider' shoulder (some tyres do differ slightly in width despite being the same technical dimensions) thus eliminating some of the stretch factor that a 265/30R19 can suffer from.